High dense sintered body of aluminum nitride, method for preparing the same and member for manufacturing semiconductor using the sintered body

ABSTRACT

The present invention provide a high dense aluminum nitride sintered body, a preparing method thereof, and a member for manufacturing semiconductor using the sintered body which has excellent leakage current characteristic, enough adsorbing property, good detachment property and excellent thermal conductivity and so can be applied to even a member for manufacturing semiconductor requiring high volume resistivity like the coulomb type electrostatic chucks as well as the Johnsen-Rahbek type electrostatic chucks.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high dense sintered body of aluminumnitride, a method for preparing the same and a member for manufacturingsemiconductor using the sintered body.

2. Description of the Prior Art

Materials mainly composed of aluminum nitride (AIN) have good thermalconductivity and insulating property so that they have been usually usedfor electrostatic chucks fixing wafers during semiconductormanufacturing process or for heaters which heat wafers during fixing inCVD process and the like.

The electrostatic chucks fix wafers using an electrostatic force and canbe classified to a Johnsen-Rahbek type and a coulomb type according totheir adsorbing way.

The Johnsen-Rahbek type electrostatic chuck generally has low volumeresistivity of about 1×10⁹˜1×10¹² Ω cm so that electric charges come tobe charged on a dielectric adsorptive surface for wafer due to such lowvolume resistivity. The electrostatic attraction between the electriccharges of the surface makes the wafer to be fixed.

Since the conventional AIN materials have low volume resistivity as wellas low relative density, they were mainly used for the Johnsen-Rahbektype electrostatic chucks having low volume resistivity.

The Johnsen-Rahbek type electrostatic chucks, however, have problem thatthe leakage current thereof is large and a wafer is hardly detached fromthe electrostatic chucks due to the remained electric charges on thesurface of the electrostatic chucks even after interrupting theapplication of direct voltage.

Meanwhile, the coulomb type electrostatic chucks fix wafers using anelectrostatic attraction between the differently charged particlespresent on the upper/lower surfaces of a dielectric. Said coulomb typeelectrostatic chucks show low leakage current and good detachmentproperty at the volume resistivity of 1×10¹⁵ Ω cm or more.

Therefore, aluminum nitride materials which can be applied to even amember for manufacturing semiconductor requiring high volume resistivitylike the coulomb type electrostatic chucks as well as the Johnsen-Rahbektype electrostatic chucks have been needed.

SUMMARY OF THE INVENTION

Accordingly, the present invention is for solving the above-mentionedproblems occurring in the prior art, and an object of the presentinvention is to provide a high dense aluminum nitride sintered body, apreparing method thereof and a member for manufacturing semiconductorusing the sintered body, which shows excellent leakage currentcharacteristic, enough adsorption property, good detachment property andexcellent thermal conductivity and so can be applied to even a memberfor manufacturing semiconductor requiring high volume resistivity likethe coulomb type electrostatic chucks as well as the Johnsen-Rahbek typeelectrostatic chucks.

In order to accomplish the above object, there is provided a high densealuminum nitride (AIN) sintered body, wherein a ratio of diffractionpeak intensity of titanium nitride (TiN) to that of AIN is 0.1 to 20%, aratio of diffraction peak intensity of magnesium aluminate (MgAl₂O₄) tothat of AIN is 0.1 to 10%, a volume resistivity thereof is 1×10¹⁵ Ω cmor more at a normal temperature and a relative density thereof is 99% ormore.

In the present invention, it is preferable that the ratio of diffractionpeak intensity of TiN to that of AIN is 0.5 to 5%.

In the present invention, it is preferable that the ratio of diffractionpeak intensity of MgAl₂O₄ to that of AIN is 0.5 to 5%.

In order to accomplish the above object, there is provided a high densealuminum nitride (AIN) sintered body, wherein powders for the AINsintered body comprise Y₂O₃ of 0.1 to 15 wt %, TiO₂ of 0.01 to 5 wt %and MgO of 0.1 to 10 wt % and the AIN sintered body has a volumeresistivity of 1×10¹⁵ Ω cm or more at a normal temperature and arelative density of 99% or more.

In the present invention, it is preferable that the powders compriseY₂O₃ of 1 to 9 wt %, TiO₂ of 0.05 to 0.5 wt % and MgO of 0.5 to 5 wt %.

In order to accomplish the above .object, there is provided a member formanufacturing semiconductor, which is composed of said high densealuminum nitride (AIN) sintered body.

In the present invention, it is preferable that the member is a coulombtype electrostatic chuck.

In order to accomplish the above object, there is provided a method forpreparing a high dense aluminum nitride (AIN) sintered body comprisingthe steps of: preparing powders for the AIN sintered body comprisingY₂O₃ of 0.1 to 15 wt %, TiO₂ of 0.01 to 5 wt % and MgO of 0.1 to 10 wt %(S1); and obtaining the AIN sintered body with a volume resistivity of1×10¹⁵ Ω cm or more at a normal temperature and a relative density of99% or more by sintering the powders and then cooling the sintered orsintering the powders and then cooling the sintered with annealing thesintered during the cooling (S2).

In the present invention, it is preferable that in the step S1, thepowders comprise Y₂O₃ of 1 to 9 wt % and/or TiO2 of 0.05 to 0.5 wt %and/or MgO of 0.5 to 5 wt %.

In the present invention, it is preferable that in the step S2, thesintering temperature is 1700 to 1850° C., more preferable 1750 to 1800°C.

In the present invention, it is preferable that in the step S2, thesintering time is 1 to 10 hours, more preferable 3 to 5 hours.

In the present invention, it is preferable that in the step S2, theannealing temperature is 1400 to 1650° C., more preferable 1450 to 1550°C.

In the present invention, it is preferable that in the step S2, theannealing time is 1 to 5 hours, more preferable 2 to 3 hours.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a variation of volume resistivity according toa variation of electric field applied to an aluminum nitride (AIN)sintered body in the first and second examples of the present invention;and

FIG. 2 is a graph showing an X-ray diffraction analysis result of analumninum nitride (AIN) sintered body in the seventh example of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a high dense aluminum nitride (AIN) sintered body, apreparing method thereof, and a member for manufacturing semiconductorusing the sintered body according to the present invention will bedescribed in detail.

In the present invention, the high dense AIN sintered body which isapplicable to a member for manufacturing semiconductor in particularsuch as a coulomb type electrostatic chuck is prepared. The AIN sinteredbody of the invention has a volume resistivity of 1×10¹⁵ Ω) cm or moreat a normal temperature and a relative density of 99% or more, whereinthe AIN sintered body comprises yttrium aluminate, titanium nitride andmagnesium aluminate which is spinel, and a ratio of diffraction peakintensity of titanium nitride (TiN) to that of AIN is 0.1 to 20%,preferably 0.5 to 5 wt % and a ratio of diffraction peak intensity ofmagnesium aluminate (MgAl₂O₄) to that of AIN is 0.1 to 10%, preferably0.5 to 5 wt %.

The high dense AIN sintered body is prepared as follows:

First, Y₂O₃ powders, TiO2 powders and MgO powders are prepared so as tothe total weight of powders before sintering can contain Y₂O₃ of 0.1 to15 wt %, TiO₂ of 0.01 to 5 wt % and MgO, which is an oxide formingspinel with aluminum oxide (Al₂O₃), of 0.1 to 10 wt %. Then, they aremixed in a solvent together with AIN powders to be dried and pulverized(S1).

If the yttrium oxide is contained below 0.1 wt %, a relative density ofAIN sintered body comes to be reduced, and if over 15 wt %, a thermalconductivity of the AIN sintered body comes to be reduced.

If the titanium oxide is contained below 0.01 wt % or over 5 wt %, avolume resistivity of the AIN sintered body comes to be reduced. Inaddition, if the magnesium oxide is contained below 0.1 wt % or over 10wt %, a volume resistivity of the AIN sintered body comes to be reduced.

In order to obtain an AIN sintered body with a volume resistivity of1×10¹⁵ Ω cm or more at a normal temperature and a relative density of99% or more, instead of the magnesium oxide, a beryllium oxide (BeO), acalcium oxide (CaO), a strontium oxide (SrO), a barium oxide (BaO), acobalt oxide (CoO), a nickel oxide (NiO) and the like can be used in thepresent invention.

Meanwhile, in order to obtain a higher volume resistivity and relativedensity, it is preferable to especially use the yttrium oxide of 1 to 9wt %, the titanium oxide of 0.05 to 0.5 wt % and magnesium oxide of 0.5to 5 wt %.

Next, the powers for the AIN sintered body prepared in the step S1 aresintered and then cooled, or sintered and then cooled with beingannealed while being cooled. To this end, a high dense AIN sintered bodyaccording to the present invention comes to be obtained (S2).

The sintering temperature is preferably 1700 to 1850° C., morepreferably 1750 to 1800° C., and the sintering time is preferably 1 to10 hours, more preferably 3 to 5 hours.

If the sintering temperature is below 1700° C., the relative densitycomes to be reduced. If the sintering temperature is over 1850° C.,economical losses come to be caused. Also, if the sintering time isbelow 1 hour, the relative density comes to be reduced. If the sinteringtime is over 10 hours, economical losses come to be caused.

The annealing temperature is preferably 1400 to 1650° C., morepreferably 1450 to 1550° C. In addition, the annealing time ispreferably 1 to 5 hours, more preferably 2 to 3 hours. The relativedensity comes to increase slightly within such range of the annealingtemperature and time.

If the annealing time is below 1 hour, a physical property afterannealing is not changed greatly compared to that before annealing. Ifthe annealing time is over 5 hours, there comes to be no more annealingeffect, which means that unnecessary costs can be caused.

The high dense AIN sintered body as prepared above has the volumeresistivity of 1×10¹⁵ Ω cm or more at a normal temperature and therelative density of 99% or more. Further, it has good leakage currentcharacteristic, enough adsorbing property, good detachment property andexcellent thermal conductivity and so can be applied to even a memberfor manufacturing semiconductor requiring high volume resistivity likethe coulomb type electrostatic chucks as well as the Johnsen-Rahbek typeelectrostatic chucks.

Hereinafter, the present invention will be described in more detail bymeans of the examples of the invention However, the present invention isnot limited to the following examples and various modifications can berealized within the scope of the appended claims. It will be understoodthat the following examples are provided to disclose the inventioncompletely and to allow those skilled in the art to carry out theinvention with ease.

PREPARATION AND EXPERIMENT

Preparation of Source Powders

Reduced nitride powders with high purity were used as AIN powders. AINpowders had a purity of 99.9% or more except oxygen and an average graindiameter of about 1.29 μm.

Y₂O₃ powders having an average grain diameter of about 0.8 μm were used.Further, TiO₂ powders having an average grain diameter of about 1 μmwere used. Also, MgO powders having an average grain diameter of about1.3 μm were used.

Such powders were mixed in the respective compositions of Table 1showing examples and Table 2 showing comparative examples.

The powders were wet-mixed for 20 hours in a solvent of anhydrousethanol using a nylon pot and an alumina ball. After mixing, the slurrywas extracted and dried at 80° C. in a drier. The dried slurry waspulverized using an alumina mortar. The pulverized powders were sievedby using an 80-mesh sieve to prepare AIN sintered body.

Hot Press Sintering

The AIN sintered powders as prepared above were placed in a graphitemold with a diameter of 40 mm. Then, the AIN sintered powders weresintered at a predetermined sintering temperature as shown in Tables 1and 2 for some time under the press pressure of 15 Mpa and the nitrogenatmosphere pressure of 0. Mpa, and then cooled or annealed while beingcooled. While cooling to a normal temperature during hot presssintering, nitrogen gas was flowed in 40 cc/min.

Evaluation of Volume Resistivity

A thickness of a specimen was based on 1 mm. A shape of an electrode wasmade to have a main electrode with a diameter of 26 mm and a guardelectrode with a diameter of 38 mm. In case of examples 1 and 2, thevolume resistivities thereof were evaluated under applied voltage of100, 250, 500 and 1000 V/mm and under the time for applying voltage of60 seconds. In case of the other examples and comparative examples, thevolume resistivities thereof were evaluated at the applied voltage of500 V/mm. In order to sufficiently remove residual charges on thesurface of the specimen in repeating the evaluation, re-evaluation wasperformed after the exposure to air for 5 minutes which follows theevaluation.

Measurement of Crystalline Phase

An X-ray diffractometer was used. The measuring condition was CuKa, 40kV, 30 mA and 2θ=5°˜80°.

Evaluation of Relative Density

The relative density was determined through dividing a bulk densityevaluated in water with Archimedes' principle by a theoretical density.

EXAMPLES

Table 1 shows source materials, sintering conditions and sintered bodycharacteristics of the examples. TABLE 1 Sintered body Source materialSintering condition characteristic condition Sintering SinteringAnnealing Annealing Relative Volume AlN Y₂O₃ TiO₂ MgO temp. time temp.time density resistivity Examples wt % wt % wt % wt % ° C. Hour ° C.Hour % Ωcm 1 96.95 1 0.05 2 1700 5 — — 99.1 1 × 10¹⁵ 2 94.95 3 0.05 21720 5 — — 99.1 2 × 10¹⁵ 3 93.8 5 0.2 1 1750 3 — — 99.5 1 × 10¹⁵ 4 88.959 2 0.05 1850 3 — — 99.5 4 × 10¹⁵ 5 94.95 3 0.05 2 1720 3 1400 5 99.4 1× 10¹⁵ 6 88.95 9 2 0.05 1850 3 1450 2 100 5 × 10¹⁵ 7 93.8 5 0.2 1 1750 31500 3 100 1 × 10¹⁵ 8 94.95 3 0.05 2 1720 5 1650 5 100 2 × 10¹⁵

Examples 1 to 8 were obtained by mixing the predetermined amounts ofyttrium oxide, titanium oxide and magnesium oxide with aluminum nitride,sintering the mixed and cooling the sintered, or sintering the mixed andcooling the sintered with annealing the sintered during the cooling.

As shown in the table 1, the AIN sintered bodies of the examples showedthe relative densities of 99% or more and the volume resistivities of1×10¹⁵ Ω cm or more.

FIG. 1 is a graph showing a variation of volume resistivity according toa variation of electric field applied to the aluminum nitride (AIN)sintered body in the first and second examples of the present invention.As shown in FIG. 1, the AIN sintered body of the examples showed stablevolume resistivities (ρ) in case that the intensity of applied voltage(E) increased.

Meanwhile a crystalline phase was checked using X-ray diffraction (XRD)analysis. FIG. 2 is a graph showing a result of XRD of the AIN sinteredbody in the example 7. As shown in FIG. 2, the sintered body of theexample contained yttrium aluminate, titanium nitride and magnesiumaluminate, which is spinel, as well as AIN as a main crystalline phase,wherein a ratio of diffraction peak intensity of TiN (200) peak to thatof AIN (100) peak was within 0.1 to 20% and a ratio of diffraction peakintensity of MgAl₂O₄ (311) peak to that of AIN (100) peak was within 0.1to 10%. cl Comparative Examples

Table 2 shows source materials, sintering conditions and sintered bodycharacteristics of the comparative examples. TABLE 2 Sintered bodySource material Sintering condition characteristic condition SinteringSintering Annealing Annealing Relative Volume Comparative AlN Y₂O₃ TiO₂MgO temp. time temp. time density resistivity Examples wt % wt % wt % wt% ° C. Hour ° C. Hour % Ωcm 1 91 9 0 0 1750 3 — — 99.7 1 × 10¹⁴ 2 95 5 00 1650 6 — — 99 5 × 10¹⁴ 3 99.6 0 0.4 0 1680 5 — — 97.8 2 × 10¹⁵ 4 91 90 0 1750 3 1500 3 99.9 1 × 10¹⁴ 5 98 0 2 0 1680 5 1450 5 98.3 3 × 10¹⁵ 699.6 0 0.4 0 1720 1 1450 1 97.6 8 × 10¹⁴ 7 99.5 0 0 0.5 1800 3 — — 100 4× 10¹³

The comparative examples 1 to 7 were different from the examples in theamounts of yttrium oxide, titanium oxide and magnesium oxide to be mixedwith the aluminum nitride and in the sintering condition.

As a result, as shown in FIG. 2, the AIN sintered body of thecomparative examples showed the volume resistivities below 1×10¹⁵ Ω cmor the relative densities below 99%. In case of such AIN sintered bodywith the volume resistivity below 1×10¹⁵ Ω cm or the relative densitybelow 99%, it is not proper to be applied to the coulomb electrostaticchucks.

Meanwhile, although the comparative example 2 showed the relativedensity of 99% due to an influence of yttrium oxide (5 wt %), it alsoshowed the volume resistivity of 5×10¹⁴ Ω cm due to the influences oftitanium oxide and magnesium oxide (respectively 0 wt %) and lowsintering temperature (1650° C.).

As described above, the AIN sintered body according to the presentinvention has good leakage current characteristic, enough adsorbingproperty, good detachment property and excellent thermal conductivity sothat it can be applied to even a member for manufacturing semiconductorrequiring high volume resistivity like the coulomb type electrostaticchucks.

1. A high dense aluminum nitride (AIN) sintered body being characterizedin that a ratio of diffraction peak intensity of titanium nitride (TiN)to that of AIN is 0.1 to 20%, a ratio of diffraction peak intensity ofmagnesium aluminate (MgAl₂O₄) to that of AIN is 0.1 to 10%, a volumeresistivity thereof is 1×10¹⁵ Ω cm or more at a normal temperature and arelative density thereof is 99% or more.
 2. A high dense aluminumnitride (AIN) sintered body being characterized in that powders for theAIN sintered body comprise Y₂O₃ of 0.1 to 15 wt %, TiO₂ of 0.01 to 5 wt% and MgO of 0.1 to 10 wt % and the AIN sintered body has a volumeresistivity of 1×10¹⁵ Ω cm or more at a normal temperature and arelative density of 99% or more.
 3. A member for manufacturingsemiconductor being composed of a high dense aluminum nitride (AIN)sintered body, wherein a ratio of diffraction peak intensity of titaniumnitride (TiN) to that of AIN is 0.1 to 20%, a ratio of diffraction peakintensity of magnesium aluminate (MgAl₂O₄) to that of AIN is 0.1 to 10%,a volume resistivity thereof is 1×10¹⁵ Ω cm or more at a normaltemperature and a relative density thereof is 99% or more.
 4. The memberfor manufacturing semiconductor according to claim 3, wherein the memberis a coulomb type electrostatic chuck.
 5. A member for manufacturingsemiconductor being composed of a high dense aluminum nitride (AIN)sintered body, wherein powders for the AIN sintered body comprise Y₂O₃of 0.1 to 15 wt %, TiO₂ of 0.01 to 5 wt % and MgO of 0.1 to 10 wt % andthe AIN sintered body has a volume resistivity of 1×10¹⁵ Ω cm or more ata normal temperature and a relative density of 99% or more.
 6. Themember for manufacturing semiconductor according to claim 5, wherein themember is a coulomb type electrostatic chuck.
 7. A method for preparinga high dense aluminum nitride (AIN) sintered body, comprising the stepsof: preparing powders for the AIN sintered body comprising Y₂O₃ of 0.1to 15 wt %, TiO₂ of 0.01 to 5 wt % and MgO of 0.1 to 10 wt % (S1); andobtaining the AIN sintered body with a volume resistivity of 1×10¹⁵ Ω cmor more at a normal temperature and a relative density of 99% or more bysintering the powders and then cooling the sintered or sintering thepowders and then cooling the sintered with annealing the sintered duringthe cooling (S2).
 8. The method according to claim 7, wherein in thestep S2, the sintering temperature is 1700 to 1850° C.
 9. The methodaccording to claim 8, wherein the sintering time is 1 to 10 hours. 10.The method according to claim 7, wherein in the step S2, the annealingtemperature is 1400 to 1650° C.
 11. The method according to claim 10,wherein the annealing time is 1 to 5 hours.